Electron beam writing equipment and electron beam writing method

ABSTRACT

Electron beam writing equipment has an electron source and an electron optics system for scanning an electron beam emitted from the electron source on a sample via deflection means having at least two different deflection speeds. An objective lens is used to form a desired pattern on the sample The electron beam is moved by high speed scanning with the deflection means to repeat formation of a patterned beam. The electron beam is moved on the mark for beam correction by low speed scanning with the deflection means in synchronization with one cycle of the repetition. The position or the deflection distance of the electron beam or blanking time is corrected using detectors for back scattered or secondary electrons.

BACKGROUND OF THE INVENTION

The present invention relates to an electron beam writing technique foruse in a manufacturing process of a semiconductor integrated circuit.More specifically, the present invention relates to high-precisionelectron beam writing equipment and writing method.

In prior art electron beam writing equipment, the size of the fastestdeflection field on a sample is about 50 μm square (for example,Sakitani et al.: Journal of Vacuum and Technology, B12, 1992, pp.2759-2763).

To deflect the 50 μm square precisely, deflection is corrected.Specifically, an electron beam is deflected to near the corner of thedeflection field to detect a mark for beam correction near it, therebymeasuring and correcting a difference between a desired deflectiondistance and an actually measured deflection distance.

Electron beam writing equipment having a micro deflection field of about2 μm square is proposed (for example, see Iwadate et al.: Journal ofVacuum and Technology, B5, 1987, pp. 75-78).

As a reliable method for making electron beam writing equipment faster,there is a multi beam method. In this method, plural electron beamsarrayed at a predetermined pitch in a two-dimensional manner are used.The distance between the electron beams is short so that the fastestdeflection field is about 2 μm square.

In the above prior art deflection correction method of 50 μm square,scanning above 2 μm is performed for mark detection itself. The priorart method cannot be applied to a 2 μm-square field. In the above priorart, a deflection correction method of such micro deflection field isnot described.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an electron beamwriting technique which can correct deflection for a micro field inelectron beam writing equipment with high precision.

To achieve the above object, the present invention has a functiondeflecting an electron beam at at least two different deflection speedsfor scanning on a sample; a function repeating formation of a patternedbeam in the electron beam by high speed scanning; a function moving theelectron beam on a mark for beam correction by low speed scanning insynchronization with its one process; and a function detecting abackscattered electron or a secondary electron from the scanned mark forbeam correction and near it or a transmission electron therethrough tocorrect the position or the deflection distance of the electron beam orblanking time from the detected result.

The method according to the present invention is particularly suitablefor multi-beam electron beam writing equipment. Correction using pluralelectron beams is effective. For example, the electron beam writingequipment has a function moving adjacent electron beams in parallel toform a patterned beam; and a function comparing the detected results ofthe plural electron beams.

In addition, the patterned beam is separately provided plural areas toperform higher-precision measurement. Further, as solving means, lowspeed scanning is performed in plural directions to change an on/offpattern of an electron beam at high speed scanning by the scanningdirection.

Representative construction examples of the present invention will belisted.

(1) Electron beam writing equipment of the present invention has: anelectron source; an electron optics system irradiating for scanning anelectron beam emitted from the electron source on a sample viadeflection means having at least two different deflection speeds and anobjective lens to form a desired pattern on the sample; a stage mountingthe sample; a mark for beam correction provided on the stage; anelectron detector detecting a backscattered electron, a secondaryelectron or a transmission electron obtained by irradiation of theelectron beam; a function moving the electron beam by high speedscanning with the deflection means to repeat formation of a patternedbeam; a function moving the electron beam on the mark for beamcorrection by low speed scanning with the deflection means insynchronization with one cycle of the repetition; and a functiondetecting a backscattered electron or a secondary electron emitted fromthe mark for beam correction and near it by the low speed scanning or atransmission electron transmitted through the mark for beam correctionto correct the position or the deflection distance of the electron beamor blanking time from the detected result.

(2) Electron beam writing equipment of the present invention has: anelectron optics system irradiating for scanning plural electron beamsarrayed at a predetermined pitch on a sample via deflection means havingplural deflectors having at least two different deflection speeds and anobjective lens to form a desired pattern on the sample; a stage mountingthe sample; a mark for beam correction provided on the stage; and anelectron detector detecting a backscattered electron, a secondaryelectron or a transmission electron obtained by irradiation of theelectron beam, wherein the deflection means has a first deflector forhigh speed scanning and a second deflector for low speed scanning, theplural electron beams are moved in parallel by high speed scanning withthe first deflector to form a patterned beam, the plural electron beamsare moved in parallel on the mark for beam correction by low speedscanning with the second deflector in synchronization with formation ofthe patterned beam, and a backscattered electron or a secondary electronemitted from the mark for beam correction and near it by the low speedscanning or a transmission electron transmitted through the mark forbeam correction is detected to correct the position or the deflectiondistance of the electron beam or blanking time from the detected result.

(3) An electron beam writing method of the present invention has thesteps of: irradiating an electron beam emitted from an electron sourceon a sample via an electron optics system having deflection means havingat least two different deflection speeds and an objective lens to form adesired pattern on the sample; high speed scanning the electron beamusing the deflection means to repeat formation of a patterned beam; lowspeed scanning the electron beam on a mark for beam correction providedon a stage mounting the sample with the deflection means insynchronization with one cycle of the repetition; detecting abackscattered electron or a secondary electron emitted from the mark forbeam correction and near it by the low speed scanning or a transmissionelectron transmitted through the mark for beam correction; andcorrecting the position or the deflection distance of the electron beamor blanking time from the detected result.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an equipment configuration according toEmbodiment 1 of the present invention;

FIG. 2 is a diagram of assistance in explaining a deflection correctedmicro field;

FIG. 3 is a diagram of assistance in explaining a scanning methodaccording to Embodiment 1 of the present invention;

FIG. 4 is a diagram showing measured results of linearity according toEmbodiment 1 of the present invention;

FIG. 5 is a diagram of assistance in explaining a scanning methodaccording to Embodiment 2 of the present invention;

FIG. 6 is a diagram showing an example of a beam profile obtained byscanning of FIG. 5;

FIGS. 7 a to 7 b are diagrams showing another example of the beamprofile; and

FIG. 8 is a diagram of assistance in explaining a scanning methodaccording to Embodiment 3 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below withreference to the drawings.

(Embodiment 1)

FIG. 1 shows the configuration of electron beam writing equipment usedin this embodiment.

An electron beam 111 emitted from an electron gun (electron source) 110is a parallel beam through a condenser lens 112, and is then dividedinto plural point beams by an aperture array 113 having pluralapertures. A lens array 114 at the later stage forms intermediate images116 of the point beams. A blanker array 115 and a blanking aperture 119are provided so as to individually switch on/off the plural point beams.

The multi point beams thus formed are condensed by a doublet lens 122having a first projection lens 118 and a second projection lens 121 tobe image formed onto a sample 124. The multi beams are distant from eachother so as to provide large field projection in which the maximumdistance of an electron beam on a pupil image is substantially longerthan the maximum distance of the electron beam on an object plane.

Between the object plane and the image plane of the doublet lens 122,there are a deflector 120 for high speed and a deflector 128 for lowspeed to define the writing position on the sample 124. On a stage 125is provided a mark 126 for detecting the position of an electron beam. Alaser interferometer, not shown, measuring the position of the stage 125and a backscattered electron detector 123 are used to measure theposition of an electron beam. In this example, the electron detectordetecting a backscattered electron or a secondary electron from the mark126 is used for measuring the position of an electron beam. An electrondetector detecting an electron transmitted through an aperture mark maybe also used.

Above the first projection lens 118 as the first lens of the doubletlens 122 are provided aligners 117 in two stages. They are engaged witheach other to adjust the incident angle and the incident position of anelectron beam upon the lens. The aligners 117 are driven by an alignercontrol circuit 104. The doublet lens 122 is driven by a lens controlcircuit 105. In this embodiment, specifically, electric currents aresupplied. The set value of each of the electric currents is decided byinformation given by a data control circuit 101. Similarly, a focuscontrol circuit 102 and a pattern generating circuit 103 supply avoltage to operate the corresponding optical device. The set values ofthese are also decided by information given by the data control circuit101. The data control circuit 101 uses information obtained from asignal handling circuit 107 and a stage control circuit 108 to performcalculation deciding the amounts of operation of the lenses and thealigners. This equipment has a display 109 having a screen making use ofthese functions to set the change of excitation, display the amount ofchange of the position of an electron beam, or reset the aligners andlens excitation currents.

As shown in FIG. 2, the pitch of multi beams 202 of this embodiment onthe sample is 2 μm. Each of the beams must write a micro field 201 of 2μm square. In this writing method, on/off of an electron beam iscontrolled during 2 μm square writing to form a pattern. To increase thethroughput, the micro field must be deflection scanned at high speed. Aspecial deflector scans it. To correct the 2 μm square deflection, thefollowing means is used.

FIG. 3 shows its scanning method. High speed scanning 301 is performedon the entire surface of the micro field 201. The two-dimensionalscanning process is repeated. Low speed scanning 303 is performed on amark for beam correction 302 of 0.1 μm circle formed on a siliconsubstrate 304 provided on the stage 125 in engagement with (insynchronization with) one process (one cycle) of the scanning process.Summation of one cycle of high speed scanning is considered, which isequal to the electron beam of 2 μm square.

The present invention is based on new findings in consideration ofsubstantially converting a deflection field to a beam shape.

As described above, in synchronization with one cycle of the repetitionprocess of the high speed scanning 301 on the entire surface of themicro field 201, two-dimensional scanning is performed on the mark forbeam correction 302 by the low speed scanning 303. A rectangular beamimage of 2 μm square can be obtained. The size of the image is measuredto perform deflection correction of the micro field.

Using the multi beam writing function, the on/off control of an electronbeam during scanning can form an electron beam image of a substantiallyarbitrary shape. Linearity of deflection can be also measured. FIG. 4shows measured results of linearity. In the drawing, the horizontal axisindicates a desired design deflection distance (μm) and the verticalaxis indicates a difference between an actually measured deflectiondistance and the design deflection distance. Deflection in the Xdirection obtains a large gain, and deflection in the Y directionobtains a small gain. The result is fed back to finally reduce an errorof the linearity below 5 nm.

Image shape measurement corresponds, not only to a rectangular pattern,but also to an arbitrary pattern. The means can inspect writing data andmeasure the limit of a blanking speed.

(Embodiment 2)

The same equipment as that of Embodiment 1 is used. A knife edge 502 asshown in FIG. 5 is used as a mark for detection. Gallium arsenide isused as the material of the knife edge 502. A Faraday cup is used todetect and differentiate a detected signal of a transmission electron,thereby obtaining a beam profile. Low speed scanning in this case issubstantially one-dimensional scanning. High speed scanning 501 isperformed on the entire surface of the micro field 201. Thetwo-dimensional scanning process is repeated. Low speed scanning 503 isperformed on the knife edge 502 in engagement with (in synchronizationwith) one process (one cycle) of the scanning process.

FIG. 6 shows a beam profile obtained by the scanning method shown inFIG. 5. In the drawing, the horizontal axis indicates a low speedscanning distance and the vertical axis indicates the signal intensityof a detected transmission electron. The resolution of the knife edge502 is sufficiently high. The tilt of the edge is caused mainly byunfocusing of the beam. This is used to adjust a stigma and a focalpoint.

In the present invention, unfocusing of the beam can be measured in thestate close to actual writing. This can obtain ±0.2 μm asreproducibility of focal point correction.

An example in which the shape of a beam image is devised is shown. FIG.7 a is an example in which the pattern of a micro field having a shape702 so as to switch on/off a beam in separately provided two areas isused for measurement in a scanning direction 703 as shown in FIG. 7 b.As a result, a beam profile 701 is divided into two crests. The distanceof its peak is measured to correct high speed deflection. Measuring thecenter of the crest can increase the precision more easily thanmeasuring the width of the crest. This is a correction method making useof the characteristic of this writing method.

In this case, in scanning in the 90° right angle direction, the onposition may be changed during high speed operation.

(Embodiment 3)

In this embodiment, plural multi beams are used. In FIG. 8, high speedscanning 801 is performed on the entire surface of the micro field 201by moving adjacent multi beams in parallel. As seen in the drawing, thiscan form a rectangular beam of about 2 μm×4 μm by high speed scanning ofone cycle. In this case, when there is an error in the construction ofthe micro field or there is an error in the pitch of the multi beams,connection of the boundary parts is not complete. In FIG. 8, thedistance between the two multi beams is short and the micro fields areoverlapped at the boundary parts to make an overlap area 804. As aresult, the intensity uniformity of the synthesized beam isdeteriorated.

This embodiment uses a backscattered electron signal produced by forminga tungsten dot 802 of 0.15 μm on the silicon thin film substrate 304 tobe low speed scanned thereon. A signal intensity distribution thusobtained is resolved to write the boundary part of the micro field withhigh precision. The origin point position of each of the multi beams iscorrected by adjusting lens excitation and the intensity of a rotatingcoil. An error of connection of the boundary areas can be below 5 nm.

Measurement using plural beams is important. The results of individuallymeasured plural beams are compared to enable adjustment and monitoringof uniformity in multi beam writing.

As described in the above embodiments in detail, the present inventioncan correct a micro field of electron beam writing equipment with highprecision. In addition, deflection scanning as the concept of thepresent invention is used for conversion to a beam shape. Variouselements such as a focal point, a stigma and an origin point positioncan be adjusted.

The present invention can realize electron beam wiring equipment andwriting method which can correct deflection for a micro field of theelectron beam writing equipment with high precision.

1-12. (canceled)
 13. Electron beam writing equipment, comprising: anelectron beam optics unit for irradiating and scanning an electron beamto a sample; a sample stage provided with a detection mark; a detectorfor detecting a secondary electron, a backscattered electron or atransmission electron generated by irradiating the electron beam to thedetection mark; a control means for correcting a position or adeflection distance of the electron beam from the detected result ofsaid detector; and means for moving a deflection field in an areaincluding the detection mark, wherein the deflection field is formed onsaid sample stage by scanning the electron beam on said sample stage.14. Electron beam writing equipment, comprising: an electron beam opticsunit for irradiating and scanning an electron beam to a sample; a samplestage for mounting the sample; a substrate including a detection mark;means for scanning the electron beam to a first area on said substrateand a second area including the detection mark on the substrate; adetector for detecting a secondary electron, a backscattered electron ora transmission electron generated by irradiating the electron beam tothe second area; a control means for correcting a position or adeflection distance of the electron beam from the detected result ofsaid detector.
 15. The electron beam writing equipment according toclaim 14, wherein said substrate is arranged on said sample stageindependently to the sample, and the first area is scanned except thedetection mark on said substrate.
 16. The electron beam writingequipment according to claim 13, further comprising: means forsynchronizing the electron beam scanning for the first area and theelectron beam scanning for the second area.
 17. The electron beamwriting equipment according to claim 13, wherein said electron beamoptics unit is multi beam optics unit.
 18. The electron beam writingequipment according to claim 13, further comprising: a blanker array anda blanking aperture are provided so as to individually switch on/offsaid electron beam optics unit.
 19. The electron beam writing equipmentaccording to claim 13, wherein said detection mark contains aperturemark or a knife edge.
 20. The electron beam writing equipment accordingto claim 13, further comprising: a signal handling circuit, whichhandles the signal intensity of the secondary electron, thebackscattered electron or the transmission electron detected with saiddetector by scanning the electron beam to the second area; and means forcorrecting the position or the deflection distance of the election beamfrom the result of said signal handling circuit.
 21. The electron beamwriting equipment according to claim 13, further comprising; a controlcircuit which corrects the position, the deflection distance of theelection beam or a blanking time.
 22. The electron beam writingequipment according to claim 13, wherein said control means is providedfor correcting the position or the deflection distance in the deflectionfield of the electron beam from the detected result of said detector.23. The electron beam writing equipment according to claim 14, furthercomprising: means for synchronizing the electron beam scanning for thefirst area and the electron beam scanning for the second area.
 24. Theelectron beam writing equipment according to claim 14, wherein saidelectron beam optics unit is multi beam optics unit.
 25. The electronbeam writing equipment according to claim 14, further comprising: ablanker array and a blanking aperture are provided so as to individuallyswitch on/off said electron beam optics unit.
 26. The electron beamwriting equipment according to claim 14, wherein said detection markcontains aperture mark or a knife edge.
 27. The electron beam writingequipment according to claim 14, further comprising: a signal handlingcircuit, which handles the signal intensity of the secondary electron,the backscattered electron or the transmission electron detected withsaid detector by scanning the electron beam to the second area; andmeans for correcting the position or the deflection distance of theelection beam from the result of said signal handling circuit.
 28. Theelectron beam writing equipment according to claim 14, furthercomprising; a control circuit which corrects the position, thedeflection distance of the election beam or a blanking time.
 29. Theelectron beam writing equipment according to claim 14, wherein saidcontrol means is provided for correcting the position or the deflectiondistance in the deflection field of the electron beam from the detectedresult of said detector.